I started this Homemade Towmater Birthday Cake with a loaf pan and two 8×11 cakes. Also used a jelly roll pan so I could add height where I wanted and made 5 cupcakes for the wheels and one for the engine piece in the middle. Then built the basic shape looking at a 3D bath toy. Carved out small details then crumb coated.
It is important to put the cake in the refrigerator after crumb coating as it makes applying the final layer of frosting quicker and smoother. I used white frosting and used basic food coloring to reach the desired colors. Bundled several long toothpicks together and sowed on a grape fruit snack for the tow hook. Also used fruit snacks for lights.
To get a smoother finish spray cake with a spray bottle filled with just water and smooth over with knife. In this picture I did not get the mirrors on but gram crackers work great!